Sustained release of a therapeutic agent from PLA-PEG-PLA nanoparticles for cancer therapy

ABSTRACT

A nanoparticle that has a membrane including a polylactide-block-poly(ethylene glycol)-block-polylactide (PLA-PEG-PLA) and a polyvinyl alcohol, a bovine serum albumin contacting the membrane on the outside of the nanoparticle, a targeting group attached to the outside of the nanoparticle, and a breast cancer therapeutic agent that is encapsulated by the membrane. A nanoparticle that consists of a membrane including a polylactide-block-poly(ethylene glycol)-block-polylactide (PLA-PEG-PLA) and a polyvinyl alcohol, a bovine serum albumin contacting the membrane on the outside of the nanoparticle, breast cancer therapeutic agent that is encapsulated by the membrane, and an anti-Her2 antibody attached to the outer surface of the nanoparticle. A range of a number average molecular weight of the PEG block is 800 Da to 3 kDa and a range of a number average molecular weight of each of the PLA blocks is from 1 kDa to 5 kDa.

BACKGROUND OF THE INVENTION Technical Field

The present invention relates to a targeted sustained releasePLA-PEG-PLA nanoparticle loaded with a breast cancer therapeutic agent.

Description of the Related Art

The “background” description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description which may nototherwise qualify as prior art at the time of filing, are neitherexpressly or impliedly admitted as prior art against the presentinvention.

Systems that deliver drugs to a patient (e.g., targeted to a particulartissue or cell type or targeted to a specific diseased tissue but notnormal tissue), or that control release of drugs has long beenrecognized as beneficial. For example, therapeutics that include anactive drug and that are capable of locating in a particular tissue orcell type e.g., a specific diseased tissue, may reduce the amount of thedrug in tissues of the body that do not require treatment. This isparticularly important when treating a condition such as cancer where itis desirable that a cytotoxic dose of the drug is delivered to cancercells without killing the surrounding non-cancerous tissue. Further,such therapeutics may reduce the undesirable and sometimes lifethreatening side effects common in anticancer therapy. For example,nanoparticle therapeutics may, due to the small size, evade recognitionwithin the body allowing for targeted and controlled delivery whilee.g., remaining stable for an effective amount of time.

Therapeutics that offer such therapy and/or controlled release and/ortargeted therapy also must be able to deliver an effective amount ofdrug. It can be a challenge to prepare nanoparticle systems that have anappropriate amount of drug associated each nanoparticle, while keepingthe size of the nanoparticles small enough to have advantageous deliveryproperties. For example, while it is desirable to load a nanoparticlewith a high quantity of therapeutic agent, nanoparticle preparationsthat use a drug load that is too high will result in nanoparticles thatare too large for practical therapeutic use. Further, it may bedesirable for therapeutic nanoparticles to remain stable so as to e.g.substantially limit rapid or immediate release of the therapeutic agent.Sustained release therapeutics may offer reduced costs in drug dosing tothe patient.

Letrozole is a water insoluble chemotherapeutic agent; it is a firstline anti-breast cancer drug. Letrozole is an FDA approved drug for thetreatment of local or metastatic breast cancer that is hormone receptorpositive or has an unknown receptor status in postmenopausal women. Itis marketed as Femara. The available dosage form currently given ishighly concentrated (2.5 mg/tablet), and it causes many adverse effectslike high cholesterol, bone effects, hepatic impairment, and otherreported adverse effects. All of these adverse effects are caused bynonspecific interactions with non-target tissue (Table 1).

TABLE 1 Occurrence of adverse side effects as a result of Femara. Grades1-4 Grades 3-4 Femara Femara N = 2448 N = 2448 Adverse Reaction n (%) n(%) Pts with any adverse event 2310 94.4 635  25.9  Hypercholesterolemia1280 52.3 11  0.4 Hot Flashes/Flushes 821 33.5 0 — Arthralgia/Arthritis618 25.2 85  3.5 Night Sweats 357 25.2 0 — Bone Fractures 338 14.6 — —Weight Increase 317 13.8 27  1.1 Nausea 283 11.6 6 0.2 Bone Fractures247 10.1 — — Fatigue (Lethargy, Malaise, Asthenia) 235 9.6 6 0.2 Myalgia217 8.9 18  0.7 Edema 164 6.7 3 0.1 Weight Decrease 140 5.7 8 0.3Vaginal Bleeding 128 5.2 1 <0.1  Back pain 125 5.1 7 0.3 OsteoporosisNOS 124 5.1 10  0.4 Bone Pain 123 5.0 6 0.2 Depression 119 4.9 16  0.7Vaginal Irritation 111 4.5 2 <0.1  Headache 105 4.3 9 0.4 Pain inextremity 103 4.2 6 0.1 Osteopenia 87 3.6 0 — Dizziness/Light headedness84 3.4 1 <0.1  Alopecia 83 3.4 0 — Vomiting 80 3.3 3 0.1 Cataract 49 2.016  0.7 Constipation 49 2.0 3 0.1 Breast Pain 37 2.0 1 <0.1  Anorexia 201.5 1 <0.1  Endometrial Hyperplasia/Cancer 11/1909 0.8 — — Endometrialproliferation Disorders 10 0.3 0 — Endometrial Hyperplasia/Cancer 6/1909 0.3 — — Other Endometrial Disorders 2 <0.1 0 — MyocardialInfarction 24 1.0 — — Myocardial Infarction 37 1.5 — — MyocardialIschemia 6 0.2 — — Cerebrovascular Accident 52 2.1 — — CerebrovascularAccident 70 2.9 — — Angine 26 1.1 — — Angina 32 1.3 — — ThromboembolicEvent 51 2.1 — — Thromboembolic Event 71 2.9 — — Other Cardiovascular1260 10.6 — — Other Cardiovascular1 312 12.7 — — Second Malignancies 532.2 — — Second Malignancies 102 4.2 — —

In view of the forgoing, one objective of the present disclosure is toprovide a nanoparticle with sustained release and targeting propertiesfor a cancer therapeutic.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect, the present disclosure relates to ananoparticle having a membrane comprising apolylactide-block-poly(ethylene glycol)-block-polylactide (PLA-PEG-PLA)copolymer and a polyvinyl alcohol polymer, a bovine serum albumincontacting the membrane on the outer surface of the membrane, a cancertargeting agent attached to the outer surface of the membrane, and abreast cancer therapeutic agent that is encapsulated by the membrane.PLA-PEG-PLA has a number average molecular weight range of the PEG blockof 800 Da to 3 kDa and a number average molecular weight range of eachof the PLA blocks of 1 kDa to 5 kDa. The nanoparticles are biocompatibleand may be useful for treating breast cancer. These nanoparticles mayalso offer sustained release of the breast cancer therapeutic agent.

In some embodiments, the polyvinyl alcohol is a weight average molecularweight from 85 kDa to 100 kDa.

In some embodiments, the polylactide-block-poly(ethyleneglycol)-block-polylactide (PLA-PEG-PLA) is 60 to 95 weight percentrelative to the total weight of the nanoparticle, and 0.5 to 5 weightpercent of polyvinyl alcohol relative to the total weight of thenanoparticle.

In some embodiments, the bovine serum albumin is 0.5 to 8 weight percentrelative to the total weight of the nanoparticle.

In some embodiments, the nanoparticle has a diameter of 300 nm to 370nm.

In some embodiments, a rate of release of the breast cancer therapeuticagent is a cumulative percent of 25% to 75% in 24 hours to 96 hours.

In some embodiments, the cancer targeting agent is an anti-Her2antibody.

In some embodiments, the anti-Her2 antibody is sourced from a rabbit.

In some embodiments, the nanoparticle has a diameter of 310 nm to 350nm.

In some embodiments, the anti-Her2 antibody is conjugated to themembrane.

In some embodiments, the breast cancer therapeutic agent is at least oneselected from the group consisting of letrozole, cetuximab, gleevac,idarubicin, trastuzumab, lapatinib, paclitaxel, and a salt thereof.

In some embodiments, the breast cancer therapeutic agent is 0.5 to 10weight percent relative to the weight of the nanoparticle.

In some embodiments, the nanoparticle has an internal volume of 1picoliter to 1 nanoliter.

In some embodiments, the nanoparticle has a zeta potential of −7 mV to−20 mV.

In some embodiments, the membrane further includes a diblock copolymer.

In some embodiments, a weight percent of the diblock copolymer relativeto the nanoparticle is 0.01% to 0.1%.

In some embodiments, the diblock copolymer has one hydrophobic polymerblock and one hydrophilic polymer block.

In some embodiments, the diblock coplymer has at least one hydrophobicpolymer block selected from the group consisting of polycaprolactone(PCL), polyvalerolactone (PVL), poly(lactide-co-glycolide) (PLGA),polylactic acid (PLA), polybutyrolactone (PBL), polyglycolide, orpolypropiolactone (PPL), and one hydrophilic polymer block selected fromthe group consisting of polyethylene glycol (PEG), hyaluronic acid (HA),or poly-γ-glutamic acid (PGA).

In some embodiments, a range of number average molecular weight range ofthe hydrophobic block and the hydrophilic block is from 800 Da to 5 kDa.

In one embodiment, the membrane is prepared by a double emulsion methodcomprising mixing a first emulsion with a second emulsion, where thefirst emulsion and the second emulsion comprise polyvinyl alcohol as anemulsifying agent.

In one embodiment, the nanoparticle consists of a membrane comprising apolylactide-block-poly(ethylene glycol)-block-polylactide (PLA-PEG-PLA)and a polyvinyl alcohol, a bovine serum albumin contacting the membraneon the outside of the nanoparticle, a breast cancer therapeutic agentthat is encapsulated by the membrane, and an anti-Her2 antibody attachedto an outer surface of the membrane. A range of a number averagemolecular weight of the PEG block is 800 Da to 3 kDa and a range of anumber average molecular weight of each of the PLA blocks is from 1 kDato 5 kDa.

The foregoing paragraphs have been provided by way of generalintroduction, and are not intended to limit the scope of the followingclaims. The described embodiments, together with further advantages,will be best understood by reference to the following detaileddescription taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1A is a schematic of a method of filling the nanoparticles with thebreast cancer therapeutic;

FIG. 1B is a schematic of a method of employing an emulsifier in themethod of filling the nanoparticles with the breast cancer therapeutic;

FIG. 2 is a graph of an exemplary release rate of a breast cancertherapeutic from the nanoparticle;

FIG. 3A is a diagram of exemplary data on the diameter of nanoparticleshaving a breast cancer therapeutic agent incorporated in to thenanoparticles and having an anti-Her2 antibody contacting the exteriorsurface of the nanoparticle;

FIG. 3B is a scatter plot of the counts of nanoparticles that are elutedfrom a dynamic light scattering chromatography column;

FIG. 4A is a scanning electron micrograph of an embodiment ofcrystallized nanoparticles prior to incorporating the breast cancertherapeutic agent into the interior space at 1,200× magnification;

FIG. 4B is a scanning electron micrograph of an embodiment ofcrystallized nanoparticles prior to incorporating the breast cancertherapeutic agent into the interior space at 24,000× magnification;

FIG. 5A is a scanning electron micrograph of crystallized nanoparticlesprior to incorporating the breast cancer therapeutic agent into theinterior space at 15,000× magnification;

FIG. 5B is a scanning electron micrograph of crystallized nanoparticlesprior to incorporating the breast cancer therapeutic agent into theinterior space at 100,000× magnification;

FIG. 6 is a scanning electron micrograph of an embodiment ofcrystallized nanoparticles after incorporating the breast cancertherapeutic agent into the interior space at 65,000× magnification;

FIG. 7A is an X-ray photoelectron spectroscopy (XPS) scan of thecrystalized surface of the nanoparticle pictures in FIG. 7B;

FIG. 7B is scanning electron micrograph of an embodiment of crystallizednanoparticles;

FIG. 8A is an XPS scan of the crystalized surface of the nanoparticlepictures in FIG. 8B;

FIG. 8B is scanning electron micrograph of an embodiment of crystallizednanoparticles;

FIG. 9A is a scanning electron micrograph of an embodiment ofcrystallized complete nanoparticles at 50,000× magnification;

FIG. 9B is a scanning electron micrograph of an embodiment ofcrystallized complete nanoparticles at 5,000× magnification;

FIG. 9C is a scanning electron micrograph of an embodiment ofcrystallized complete nanoparticles at 70,000× magnification;

FIG. 10 is a scanning electron micrograph of an embodiment ofcrystallized nanoparticles after incorporating the breast cancertherapeutic agent into the interior space at a 700× magnification;

FIG. 11A is a XPS of the crystalized surface of the nanoparticlepictures in FIG. 11B;

FIG. 11B is a scanning electron micrograph of an embodiment ofcrystallized nanoparticles;

FIG. 12A is a XPS of the crystalized surface of the nanoparticlepictured in FIG. 12B;

FIG. 12B is a scanning electron micrograph of an embodiment ofcrystallized nanoparticles;

FIG. 13 is a Fourier Transform Infrared spectrum of an embodiment ofnanoparticles prior to incorporating the breast cancer therapeutic agentinto the interior space;

FIG. 14 is a scanning electron micrograph of an embodiment ofcrystallized nanoparticles after incorporating the breast cancertherapeutic agent into the interior space at 250,000× magnification;

FIG. 15 is a scanning electron micrograph of an embodiment ofcrystallized nanoparticles after incorporating the breast cancertherapeutic agent into the interior space at 150,000× magnification;

FIG. 16 is a scanning electron micrograph of an embodiment ofcrystallized nanoparticles after incorporating the breast cancertherapeutic agent into the interior space at 65,000× magnification;

FIG. 17 is a scanning electron micrograph of an embodiment ofcrystallized nanoparticles after incorporating the breast cancertherapeutic agent into the interior space at 120,000× magnification;

FIG. 18 is a scanning electron micrograph of an embodiment ofcrystallized nanoparticles after incorporating the breast cancertherapeutic agent into the interior space at 120,000× magnification;

FIG. 19 is a graph showing the correlation between the concentration ofPVA and the particle size;

FIG. 20 is a graph showing the expression of MAPK3 gene in the presenceof encapsulated Letrozole and free Letrozole; and

FIG. 21 is a graph showing the expression of c-MYC gene in the presenceof encapsulated Letrozole and free Letrozole.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present disclosure relates to a nanoparticle having a membranecomprising a polylactide-block-poly(ethylene glycol)-block-polylactideblock (PLA-PEG-PLA) copolymer and a polyvinyl alcohol polymer, a bovineserum albumin contacting an outer surface of the membrane (i.e.contacting the outside surface of the nanoparticle), a cancer targetingagent contacting the outer surface of the membrane, and a breast cancertherapeutic agent that is encapsulated by the membrane.

The PLA-PEG-PLA polymer is a triblock copolymer. Block copolymers aremade up of different polymerized monomers covalently bonded in segments.In the PLA-PEG-PLA polymer, there are three blocks, a first PLA block, aPEG block, and a second PLA block, which together make a triblockcopolymer. The PLA-PEG-PLA copolymer of the present disclosure may havea number average molecular weight range of the PEG block of from 800 Dato 3 kDa, from 1.5 kDa to 2.5 kDa, or from 1.75 kDa to 2.25 kDa. Anumber average molecular weight range of the first PLA block is in arange of from 1 kDa to 5 kDa, from 1.5 kDa to 4.5 kDa, from 2 kDa to 4kDa, from 2.5 kDa to 3.5 kDa, or from 2.75 kDa to 3.25 kDa. A numberaverage molecular weight range of the second PLA block is a range offrom 1 kDa to 5 kDa, from 1.5 kDa to 4.5 kDa, from 2 kDa to 4 kDa, from2.5 kDa to 3.5 kDa, or from 2.75 kDa to 3.25 kDa. The first PLA blockand the second PLA block may have different number average molecularweights relative to each other.

The PLA blocks of the copolymer are hydrophobic, and the PEG block ishydrophilic. The membrane of the nanoparticle comprises the copolymer.Spherical structures formed by the PLA-PEG-PLA copolymer, which may bereferred to as polymersomes, have an interior space, and interiorsurface, an intermembrane space, and an exterior surface. Thepolymersome is a hollow spherical shape having synthetic polymers thatencircle the circumference of the spherical shape. In the polymersome,the hollow center is the interior space of the polymersome. The membraneenclosing the sphere has an exterior facing portion, the exteriorsurface of the polymersome, and an interior facing portion, the interiorsurface of the polymersome. The span between the exterior surface andthe interior surface of the polymersome is the intermembrane space. Thepolymersome formed may tend to have a hydrophobic exterior surface andinterior membrane, whereas an intermembrane space, formed by the PEGblock, will be hydrophilic. In some embodiments, the PLA-PEG-PLAcopolymer is 60 to 95 weight percent or 70 to 85 weight percent,relative to the total weight of the nanoparticle. In some embodiments, amembrane thickness, or a span of the intermembrane space may be from 120nm to 2 microns, from 250 nm to 1.75 microns, from 0.5 microns to 1.5microns, from 0.75 microns to 1.25 microns, or from 1 micron to 1.1microns.

In some embodiments of the nanoparticle, the membrane may furtherinclude a diblock copolymer (i.e. two blocks of polymers). In someembodiments, a weight percent of the diblock copolymer relative to thetotal weight of the nanoparticle is 0.01% to 0.1%, 0.05% to 0.08%, or0.06% to 0.07%. In some embodiments, the diblock copolymer has onehydrophobic block and one hydrophilic block. In some embodiments, theratio of the number average molecular weight range of the hydrophobicblock and the hydrophilic block is from 800 Da:1 kDa to 3 kDa:5 kDa, 1kDa:2 kDa to 4 kDa:5 kDa, 1.5 kDa:2 kDa to 4.5 kDa:5 kDa. In someembodiments, the diblock coplymer has at least one hydrophobic blockselected from the group consisting of polycaprolactone (PCL),polyvalerolactone (PVL), poly(lactide-co-glycolide) (PLGA), polylacticacid (PLA), polybutyrolactone (PBL), polyglycolide, or polypropiolactone(PPL), and one hydrophilic polymer selected from the group consisting ofpolyethylene glycol (PEG), hyaluronic acid (HA), or poly-γ-glutamic acid(PGA). Exemplary combinations of diblock copolymers may include, but arenot limited to PCL-PEG, PLGA-HA, PVL-PGA, PBL-PEG, and PPL-HA. In someembodiments, the nanoparticle membrane may include one or more diblockcopolymers. Employing the diblock copolymer may improve solubility ofthe breast cancer therapeutic agent in the interior space of thenanoparticle.

In some embodiments of the membrane, the polyvinyl alcohol (PVA) polymeris an emulsifying agent. The polyvinyl alcohol polymer may be employedto promote a fluid membrane of the nanoparticle. The amount of polyvinylalcohol directly relates to a viscosity of the membrane. The viscosityof the membrane may contribute to a release rate of the breast cancertherapeutic agent from the nanoparticle and may be changed based on adesired release rate of the breast cancer therapeutic agent. Themembrane viscosity of the presently described nanoparticle may be 3mPa·s to 6 mPa·s or 4 mPa·s to 5 mPa·s at 25° C. and 1 atm. Theviscosity may be measured by EPR or fluorescence spectroscopy. Thepolyvinyl alcohol employed in the nanoparticle may have a weight averagemolecular weight from 85 kDa to 100 kDa or 90 kDa to 95 kDa, and from0.25 to 5 weight percent, 1 to 4 weight percent, or 2 to 3 weightpercent of polyvinyl alcohol (PVA), relative to the total weight of thenanoparticle. The concentration of the PVA may affect the particle sizeand/or the drug release profile. When the concentration of the PVA is ina range of 0.25 to 0.75 wt %, the average particle size may range from100-115 nm and the polydispersity of the particles may range from0.23-0.25. When the concentration of the PVA is in a range of 0.76 to1.9 wt %, the average particle size may range from 116-140 nm and thepolydispersity of the particles may range from 0.20-0.225. When theconcentration of the PVA is in a range of 1.91 to 2.9 wt %, the averageparticle size may range from 141-180 nm and the polydispersity of theparticles may range from 0.15-0.199. When the concentration of the PVAis in a range of 2.91 to 5 wt %, the average particle size may rangefrom 181-200 nm and the polydispersity of the particles may range from0.12-0.149.

In some embodiments of the nanoparticle, the breast cancer therapeuticagent may include, but is not limited to letrozole, cetuximab, gleevac,idarubicin, trastuzumab, lapatinib, paclitaxel, and/or a salt thereof.In one embodiment, the breast cancer therapeutic agent is notmethotrexate. In another embodiment, the breast cancer therapeutic agentis not paclitaxel. In another embodiment, the breast cancer therapeuticagent is not doxorubicin. The nanoparticle may include a mixture ofbreast cancer therapeutic agents. The breast cancer therapeutic agentsmay be incorporated into the nanoparticle by emulsification byultrasonication of the triblock copolymers in solution. FIG. 1A depictsa schematic of a method of filling the nanoparticles with the breastcancer therapeutic. In FIG. 1A and FIG. 1B the PVA may be employed as anadded emulsifying agent or emulsifier. The PVA may interact with thedrug to allow for a reduced interfacial tension between the drug and thetriblock polymer in solution. The PVA may allow for the drug to moreeasily be encapsulated by the triblock polymer. In some embodiments, thePVA plays a dual role as an emulsifier and as a stabilizing agent. Inone embodiment, the presently disclosed nanoparticle is formed by adouble emulsion method which includes a drug and water miscible solventmixture in a mostly oily solution, followed by adding an emulsifier,such as PVA, to the solution. Then the drug and water miscible solventare diluted into a mostly aqueous solution, the action may encapsulatethe drug inside a mostly oily membrane assisted by the emulsifier andthe drug inside the membrane can be removed from the aqueous solution.This method of preparation provides for a slow release rate of a drugfrom the membrane due to the PVA stabilizing the membrane and solventinteraction. For example, to accomplish a double emulsion there is afirst and second emulsion. A first mixture of the triblock polymers, thedrug, and a 0.5% to 5%, 0.75% to 4%, or 1% to 2% final concentration ofPVA may be combined in a solution (first emulsion). The first mixturemay then be diluted by 10 times to 30 times with a 5% to 40%, 10% to30%, or 15% to 20% lower concentration of PVA in an aqueous solution(second emulsion), then mixed and evaporated to form the finalnanoparticles. The mixing may be by ultrasonication, sonication, ormechanical mixing and obtaining the final solid nanoparticles by, forexample, centrifugation and removal of solvents, by siphoning,evaporation or both.

By the method of emulsification by ultrasonication, the breast cancertherapeutic agent is incorporated into the nanoparticle at 0.5 to 10weight percent, 1 to 8 weight percent, 3 to 7 weight percent, or 4 to 6weight percent, relative to the nanoparticle. The quantity of the breastcancer therapeutic that is required for the treatment may be dictated bythe efficiency by which the nanoparticle is retained in a breast cancerpatient's blood and the drug release rate of the nanoparticle. In someembodiments, the nanoparticle has an internal volume of 1 picoliter to 1nanoliter, 10 picoliter to 750 picoliter, 100 picoliter to 500picoliter, or 250 picoliter to 400 picoliter. In some embodiments, arate of release of the breast cancer therapeutic agent is a cumulativepercent of volume, relative to the total incorporated breast cancertherapeutic agent in the nanoparticle, 25% to 75%, 35% to 65%, or 45% to55% in 24 hours to 96 hours, 36 hours to 72 hours, 48 hours to 60 hours.FIG. 2 depicts a graph of an exemplary release rate of a breast cancertherapeutic agent from the nanoparticle. In some embodiments within 24hours 10%-40% of the drug volume may be released in a patient. Thebreast cancer therapeutic agent may be released through the pores of themembrane. The pores of the membrane may have a diameter in a range of0.1-10 nm, 0.5-10 nm, 1-9 nm, 2-8 nm, or 3-6 nm.

The presently disclosed nanoparticle may be stable for storage for 100to 130 days. The nanoparticles may be stored in water (e.g., distilledwater, deionized water, doubly distilled water) and kept at atemperature in a range of 0-10° C., 0-5° C., or 3-5° C. The presentlydisclosed nanoparticle, which is optionally loaded with the breastcancer therapeutic agent, may have a polydispersity of, for example, 0.1to 0.2, 0.12 to 0.18, or 0.14 to 0.16.

The polymersome as described herein has a hydrophobic exterior surface.The hydrophobic exterior surface may not be easily solubilized in an invivo application by injection into the blood stream of a cancer patient.To increase solubility of the nanoparticle, a bovine serum albumin (BSA)is included in the presently disclosed nanoparticle. BSA is a proteinderived from cows, having 583 amino acid residues in length and amolecular weight of 66.5 kDa. In some embodiments, the BSA is, relativeto the total weight of the nanoparticle, 0.5 to 8 weight percent, 1 to 7weight percent, 2 to 6 weight percent, or 3 to 5 weight percent. The BSAmay contact the exterior membrane of the polymersome or the outside ofthe nanoparticle. The contact may be by non-specific interactions or vander Waals interactions between non-polar amino acids on the surface ofthe BSA protein and the hydrophobic PLA copolymer block. Embodiments ofthe nanoparticle prior to incorporating the breast cancer therapeuticagent into the interior space (FIG. 3), may have a diameter of 100 nm to170 nm, 110 nm to 160 nm, 125 nm to 150 nm, or 135 nm to 140 nm.Embodiments of the nanoparticle after incorporating the breast cancertherapeutic agent into the interior space (FIG. 4) may have a diameterof 190 nm to 210 nm, or 200 nm to 205 nm. Embodiments of thenanoparticle having the BSA on the exterior surface (FIG. 5), may have adiameter of 290 nm to 312 nm, 295 nm to 310 nm, or 300 nm to 305 nm.Embodiments of the nanoparticle having the BSA on the exterior surfaceand the breast cancer therapeutic agent in the interior space may have adiameter of 130 nm to 170 nm, or 140 nm to 160 nm (FIG. 6). Thepolydispersity of such nanoparticles may be in a range of 0.2-0.6,0.2-0.5, 0.2-0.4, or 0.25-0.35.

Aggregation may result in an ineffective nanoparticle for drug delivery.Zeta potential is the measurement of an electrical potential of theexterior surface of a nanoparticle. A higher (more negative) electricalpotential of the exterior surface may prevent nanoparticle aggregationby creating an electronic barrier (electrostatic repulsion) betweennanoparticles. An absolute value of electrical potential or zetapotential directly correlates to the non-aggregating potential of thenanoparticle. The presently disclosed nanoparticle has a zeta potentialof −7 mV to −20 mV, −10 mV to −18 mV, or −12 mV to −15 mV. FIG. 7 andFIG. 8 depict tables of the zeta potentials of nanoparticles prior toincorporating the breast cancer therapeutic agent into the interiorspace and the zeta potential of the nanoparticles after the breastcancer therapeutic agent is incorporated into the interior space,respectively.

The presently disclosed nanoparticle may further include a cancertargeting agent. A cancer targeting agent may be biologically activemacromolecules (e.g., monoclonal antibodies such as bevacizumab,cetuximab, or ipilimumab) or small molecules (e.g. folate). Smallmolecules may be recognized by surface protein receptors that areuniquely expressed or overexpressed on cancer tumors or in tumor relatedtissues or may be targeted to proteins and receptors inside the cancercell, such as seliciclib, imatinib, or bortezomib. Macromolecules mayrecognize surface proteins and peptides that are uniquely expressed oroverexpressed on cancer tumors or in tumor related tissues.

In some embodiments, the cancer targeting agent is an anti-Her2 antibodycontacting the outer surface or exterior surface of the nanoparticle.Her2 is a growth factor receptor and biomarker for certain aggressivebreast cancers. Her2 may be overexpressed in 15% to 30% of breastcancers. As used herein “antibody” or “antibodies” may include a fullantibody including the heavy and light chains or only portions of thefull antibody such as only a heavy chain, only a light chain, or onlythe functional antigen-binding (Fab) domains. The anti-Her2 antibody maybe monoclonal or polyclonal. The anti-Her2 antibody may be sourced froma mouse, a rabbit, a chicken, or combinations thereof.

In one embodiment, the antibody may be covalently attached to thenanoparticle membrane by a biotin-avidin complex. Biotin may be attachedto the triblock copolymers via an ester bond with biotin, and avidin maylabel the antibody. The avidin-biotin complex is the strongest knownnon-covalent interaction (K_(d)=10⁻¹⁵ M) between a protein and ligand.The bond formation between biotin and avidin is very rapid, and onceformed, is unaffected by extremes of pH, temperature, organic solventsand other denaturing agents. Avidin may further be monovalent (i.e.binding site for one biotin molecule) or divalent (i.e. two bindingsites for one biotin molecule each) for the present application, howeveravidin may have up to tetravalency. Relevant to the present disclosure,for example, a divalent avidin may be attached to an anti-Her2 antibodyvia a biotin on the anti-Her2 antibody, purified, and then mixed withthe polymersome having a biotin conjugated to a triblock copolymer bychemical methods familiar to those in the art. Other mechanisms ofattaching antibodies to the copolymers include thiolation of antibodieswith 3-(2-pyridyldithio)propionic acid-N-hydroxysuccinimide ester(SPDP), followed by deprotection with dithiothreitol (DTT) andconjugation to the triblock copolymers covalently bonded to maleimide.Additional methods familiar in the art may be used as well. See AntibodyConjugation Methods for Active Targeting of Liposomes, Chapter 4 of“Methods in Molecular medicine. Vol. 25: Drug Targeting: Strategies,Principles, and Applications,” Edited by G. E. Francis and C. Delgado ©Humana Press Inc. Totawa, N.J., incorporated by reference herein in itsentirety. Antibody attached to triblock copolymers may be a percentageby weight relative to the total nanoparticle of 25%-75%, 30%-60%, or40%-50%.

In some embodiments, the anti-Her2 antibody may contact a surface of thenanoparticle by non-specific molecular interactions or van der Waalsinteractions. The coupling by non-specific interaction may beaccomplished by combining a 15% to 25% or 18% to 20% by volume ofanti-Her2 antibody in solution with nanoparticles of 5.5×10⁻⁴ to 7×10⁻⁴particles/mL, or 6×10⁻⁴ to 6.5×10⁻⁴ particles/mL and mixed in a shakerfor 10-120 mins, 30-90 mins, or 50-70 mins at 20-50° C., 30-50° C., or35-45° C. The volume of anti-Her2 antibody in solution may be in a rangeof 10-200 μL, 10-100 μL or 40-60 μL. The volume of the nanoparticlessolution may be in a range of 100-300 μL, 150-250 μL, or 175-225 μL. Thenanoparticles/anti-Her2 mixture may be dialyzed for one hour to sixhours or two hours to four hours to remove the excess anti-Her2 antibodyby employing a single sided dialysis chamber and a nitrocellulosemembrane cut off of from 250 kDa-300 kDa. The dialysis buffer may be apH of 6.25 to 7.25, and a phosphate based buffer, such as PBS. Thebuffer may be exchanged three times every 1.5 hours to two hours.

Another aspect of the disclosure relates to a method of down regulatingexpression of a gene in a breast cancer cell line (e.g., MCF-7, 600MPE,AU565, BT-20, BT-474, BT-483, BT-549, Evsa-T, Hs578T, MDA-MB-231, SkBr3,and T-47D). The breast cancer cells may be incubated with thedrug-loaded nanoparticles for 4-100 hours, 10-90 hours, 20-80 hours, or30-75 hours. The concentration of the drug-loaded nanoparticles mayrange from 0.0001-10 μM, 0.0005-1 μM, 0.001-0.5 μM, or 0.002-0.1 μM.

Exemplary genes include antiapoptotic genes such as Bcl-2, Bcl-XL,Mc1-1, CED-9, A1, Bfl-1, MAPK3, and c-MYC. Pre-designed primers for thegenes of interest may be commercially available. Real-time PCR for theantiapoptotic genes may be performed to ensure the delivery of the drugby the nanoparticles. The gene expression levels may be quantitatedusing the delta-delta CT (ΔΔ^(CT)) method and optionally furtherre-calculated manually. The gene expression level may be normalized to ahousekeeping gene: glyceraldehydes-3-phosphate dehydrogenase (GAPDH).The gene expression level may range from −1 to +0.1, −0.8 to −0.1, −0.7to −0.2, or −0.5 to −0.3.

The nanoparticle including the antibody contacting the exterior surfacemay have a diameter of 300 nm to 370 nm, 310 nm to 350 nm, or 325 nm to340 nm (FIG. 3A and FIG. 3B). The polydispersity of such nanoparticlesmay be in a range of 0.2-0.6, 0.3-0.6, 0.3-0.5, or 0.4-0.5.

FIG. 4A and FIG. 4B depict scanning electron micrographs of anembodiment of crystallized nanoparticles prior to incorporating thebreast cancer therapeutic agent into the interior space at 1,200×magnification and 24,000× magnification. FIG. 5A and FIG. 5B depictscanning electron micrographs of crystallized nanoparticles prior toincorporating the breast cancer therapeutic agent into the interiorspace at 15,000× magnification and 100,000× magnification. FIG. 6depicts scanning electron micrographs of an embodiment of crystallizednanoparticles after incorporating the breast cancer therapeutic agentinto the interior space at 65,000× magnification.

FIG. 7A and FIG. 8A are X-ray photoelectron spectroscopy (XPS), or asurface-sensitive quantitative spectroscopic technique, that measuresthe elemental composition of the crystalized surface of the nanoparticlepictures in FIG. 7B and FIG. 8B, respectively.

FIG. 9A, FIG. 9B, and FIG. 9C depict scanning electron micrographs of anembodiment of crystallized complete nanoparticles at 50,000×magnification, 5,000× magnification, and 70,000× magnification,respectively. FIG. 10 depicts a scanning electron micrograph of anembodiment of crystallized nanoparticles after incorporating the breastcancer therapeutic agent into the interior space at a 700×magnification.

FIG. 11A and FIG. 12A are X-ray photoelectron spectroscopy (XPS), or asurface-sensitive quantitative spectroscopic technique, that measuresthe elemental composition of the crystalized surface of the nanoparticlepictures in FIG. 11B and FIG. 12B, respectively.

FIG. 13 is a Fourier Transform Infrared spectrum of an embodiment ofnanoparticles prior to incorporating the breast cancer therapeutic agentinto the interior space.

FIGS. 14, 15, 16, 17, and 18 are scanning electron micrographs of anembodiment of crystallized nanoparticles after incorporating the breastcancer therapeutic agent into the interior space at 250,000×magnification, 150,000× magnification, 65,000× magnification, 120,000×magnification, and 120,000× magnification, respectively. Themeasurements displayed in FIG. 18 represent the diameter (in nanometers)of the crystallized nanoparticles located on a main crystal.

FIG. 19 shows the variation of PVA concentrations and its effect onparticle size.

FIGS. 20 and 21 show the gene expression results. In FIG. 20, each barrepresents the expression of MAPK3 gene in the presence of each sample.In FIG. 21, each bar represents the expression of c-MYC gene in thepresence of each sample.

The presently disclosed nanoparticle may be administered to a patientfrom once weekly to four times weekly or two times weekly to 3 timesweekly at a therapeutically effective amount. Preferably, thenanoparticle is administered twice weekly (e.g., every 3 days). Thenanoparticles may be administered intravenously or intra-arterially. Insome implementations, a pharmaceutical composition of the presentlydisclosed nanoparticle may include injectable preparations. For example,sterile injectable aqueous or oleaginous suspensions may be formulatedaccording to the known art using suitable dispersing or wetting agentsand suspending agents. The sterile injectable preparation may also be asterile injectable solution, suspension, or emulsion in a nontoxicparenterally acceptable diluent or solvent, for example, as a solutionin 1,3-butanediol. Among the acceptable vehicles and solvents that maybe employed are water, Ringer's solution, U.S.P., and isotonic sodiumchloride solution. In addition, sterile, fixed oils are conventionallyemployed as a solvent or suspending medium. For this purpose any blandfixed oil can be employed including synthetic mono- or diglycerides. Inaddition, fatty acids such as oleic acid are used in the preparation ofinjectables. In one embodiment, the inventive conjugate is suspended ina carrier fluid comprising 1% (w/v) sodium carboxymethyl cellulose and0.1% (v/v) TWEEN™ 80. The injectable formulations can be sterilized, forexample, by filtration through a bacteria-retaining filter, or byincorporating sterilizing agents in the form of sterile solidcompositions which can be dissolved or dispersed in sterile water orother sterile injectable medium prior to use. In some embodiments, thenanoparticles may be applied directly to the surface of a tumor or anarea of tissue surrounding an excised tumor of a patient on a surgicalbed by a surgeon. The nanoparticles may be sprayed in a solution ordispersed by a brush, dropper, or paste onto the surface of a tumor orto the area of tissue surrounding an excised tumor during a surgicalprocedure in a living patient. The surgeon may inject the nanoparticlesin a sterile solution, as described herein, into a blood vessel enteringa tumor.

In certain embodiments of the presently disclosed nanoparticle, a“therapeutically effective amount” of the nanoparticle is that amounteffective for treating, alleviating, ameliorating, relieving, delayingonset of, inhibiting progression of, reducing severity of, and/orreducing incidence of one or more symptoms or features of breast cancer.

In some implementations of therapeutic protocols involve administering atherapeutically effective amount of the presently disclosed nanoparticleto a healthy individual (i.e., a subject who does not display anysymptoms of cancer and/or who has not been diagnosed with cancer). Forexample, healthy individuals may be injected with the nanoparticle priorto development of cancer and/or onset of symptoms of cancer; at riskindividuals (e.g., patients who have a family history of cancer;patients carrying one or more genetic mutations associated withdevelopment of cancer; patients having a genetic polymorphism associatedwith development of cancer; patients infected by a virus associated withdevelopment of cancer; patients with habits and/or lifestyles associatedwith development of cancer; etc.) can be treated substantiallycontemporaneously with (e.g., within 48 hours, within 24 hours, orwithin 12 hours of) the onset of symptoms of cancer. Of courseindividuals known to have cancer may receive inventive treatment at anytime.

In other embodiments, the nanoparticles described herein can be used toinhibit the growth of cancer cells, e.g., breast cancer cells. As usedherein, the term “inhibits growth of cancer cells” or “inhibiting growthof cancer cells” refers to any slowing of the rate of cancer cellproliferation and/or migration, arrest of cancer cell proliferationand/or migration, or killing of cancer cells, such that the rate ofcancer cell growth is reduced in comparison with the observed orpredicted rate of growth of an untreated control cancer cell. The term“inhibits growth” can also refer to a reduction in size or disappearanceof a cancer cell or tumor, as well as to a reduction in its metastaticpotential. Preferably, such an inhibition at the cellular level mayreduce the size, deter the growth, reduce the aggressiveness, or preventor inhibit metastasis of a cancer in a patient. Those skilled in the artcan readily determine, by any of a variety of suitable indicia, whethercancer cell growth is inhibited.

Inhibition of cancer cell growth may be evidenced, for example, byarrest of cancer cells in a particular phase of the cell cycle, e.g.,arrest at the G2/M phase of the cell cycle. Inhibition of cancer cellgrowth can also be evidenced by direct or indirect measurement of cancercell or tumor size. In human cancer patients, such measurementsgenerally are made using well known imaging methods such as magneticresonance imaging, computerized axial tomography and X-rays. Cancer cellgrowth can also be determined indirectly, such as by determining thelevels of circulating carcinoembryonic antigen, prostate specificantigen or other cancer-specific antigens that are correlated withcancer cell growth. Inhibition of cancer growth is also generallycorrelated with prolonged survival and/or increased health andwell-being of the subject.

The presently disclosed nanoparticle, may first interact with a cancertumor expressing the Her2 receptor. For example, the presently disclosednanoparticle while circulating in the blood stream may interactspecifically with a tumor or cell proximal to a tumor expressing theHer2 receptor. In some implementations, such as a surgeon dispersing thenanoparticles directly on to a tumor in a surgical bed of a patient, thenanoparticles coupled to the anti-Her2 antibody may recognize a Her2receptor on a cell on the surface of the tumor. The antibody againstHer2 on the surface of the antibody may interact with the Her2 receptoron the cell and become internalized into an endosome or lysosome uponbinding the cell. Once internalized the nanoparticle may begin torelease the drug into the cell lysosome or endosomes. In someembodiments, the nanoparticle may not release the drug until thenanoparticle is in the intracellular space and cannot release the drugin an endosome or lysosome. The nanoparticle may persist in the cell andslowly release the drug over duration as described herein.

The examples below are intended to further illustrate the preparation ofthe nanoparticles and are not intended to limit the scope of the claims.

Example 1

Materials

Polylactide-block-poly(ethylene glycol)-block-poly lactide triblock (PLAaverage Mn=1,500, PEG average Mn=900), Letrozole (Mw=285, 30 g),chloroform, poly(vinylalcohol) (Mw=89,000-98,000; 99% hydrolyzed),bovine serum albumin (lyophilized powder ≥96%), and Anti-Her2 producedin rabbit were obtained from Sigma-Aldrich and were used as received.

Equipment

Probe sonicator (UltraSonic Processor, Sonic VCX 130)

Centrifuge (Thermo Scientific Centrifuge)

Particle size analyzer (Brookhaven instruments)

Zetasizer

UV Spectrophotometer (Thermo-Evolution UV 60S, Thermo Scientific)

Rotary Evaporator (Buchi)

Synthesis of PEG-PLA nanoparticles, Polylactide-block-poly(ethyleneglycol)-block-polylactide

Void PEG-PLA nanoparticles were synthesized using 10 mg PEG-PLA: 10.5 mgwas dissolved in 1 ml chloroform. 200 ul of DMSO was added andultrasonication was performed (100%, 30 s). 2 ml of 3% PVA was thenadded and ultrasonication was performed (100%, 30 s). The solution wasthen diluted with 20 ml of 0.3% PVA. The 22 ml was then divided into11×2 ml to be centrifuged in the mini spin. Tubes were then centrifugedat 11,000 rpm for 1 hour. Pellet was then washed 3 times as following:supernatant was decanted, 1 ml of distilled water was added,ultrasonication was performed (70%, 5 s), and then centrifuged for 1hour at 11,000 rpm. After the final washing step, supernatant wasdiscarded and pellet were left to dry. Water was then added to thepellets to be dissolved, and nanoparticles solution was collected in a50 ml falcon tube and stored at 4° C. Data of exemplary voidnanoparticles are exhibited in Table 2 and Table 3.

TABLE 2 Exemplary empty/void nanoparticle (NP) data Eff. Diam. Poly-Baseline Type Sample ID (nm) dispersity Index DLS void NPs soln 002 - 5146.02 0.18 4.04 DLS void NPs soln 002 - 4 152.07 0.17 2.47 DLS void NPssoln 002 - 3 151.06 0.21 1.14 DLS void NPs soln 002 - 2 150.37 0.16 0.92DLS void NPs soln 002 - 1 150.89 0.16 1.23 Mean: 150.08 0.18 1.96 StdErr: 1.05 0.01 0.59 Std Dev: 2.35 0.02 1.31

TABLE 3 Exemplary empty/void nanoparticle data on zeta potential ZetaMobility Potential (μ/s)/ RMS Type Sample ID (mV) (V/cm) Residual PALSvoid NPs soln 002 - 5 −17.45 −1.36 3.01E−02 PALS void NPs soln 002 - 4−17.31 −1.35 1.48E−02 PALS void NPs soln 002 - 3 −19.32 −1.51 2.43E−02PALS void NPs soln 002 - 2 −16.50 −1.29 2.65E−02 PALS void NPs soln002 - 1 −22.65 −1.77 2.07E−02 Mean: −18.64 −1.46 2.33E−02 Std Err: 1.100.09 2.61E−03 Std Dev: 2.47 0.19 5.84E−03Synthesis of Letrozole-Loaded Nanoparticles

To prepare Letrozole-loaded nanoparticles, a 15.2 mg (±0.1) of thepolymer was weighed and dissolved in 1 mL chloroform (CHCl₃) solvent. Asolution of Letrozole was prepared by dissolving 4.3 mg (±0.1) ofLetrozole in 4 mL of DMSO. A 200 μL of Letrozole solution was emulsifiedin the polymer solution by ultrasonication using 2 mm probe (30 s, 100%power). 2.0 mL of 3% PVA was added to the solution and also wasemulsified by ultrasonication using 2 mm probe (30 s, 100% power). Theresulted emulsion was then diluted by adding 20 mL of 0.3% PVA. Theobtained white emulsion solution was divided over 14 (1.5 mL) Eppendorftubes and was centrifuged for one hour on 11,000 rpm. The obtained whiteprecipitate was then washed and centrifuged for one hour on 11,000 rpmthree times. After the third wash the obtained pellets were left to dryand then collected, weighed and stored at 4° C. fridge. Data ofexemplary void nanoparticles are exhibited in Table 4 and Table 5.

TABLE 4 Exemplary Letrozole-loaded nanoparticle data Eff. Diam. Poly-Baseline Type Sample ID (nm) dispersity Index DLS Letrozole-loaded NPs002 - 5 209.82 0.18 0.00 DLS Letrozole-loaded NPs 002 - 4 207.39 0.150.70 DLS Letrozole-loaded NPs 002 - 3 197.52 0.12 0.00 DLSLetrozole-loaded NPs 002 - 2 195.88 0.14 2.94 DLS Letrozole-loaded NPs002 - 1 195.95 0.14 4.28 Mean: 201.31 0.15 1.59 Std Err: 3.02 0.01 0.86Std Dev: 6.75 0.02 1.93

The zeta potential and the electrophoretic mobility were measured usinga ZetaPALS potential analyzer (Brookhaven instruments, Holtsville, N.Y.,USA). The results are displayed in Table 5. The zeta potentials ofLTZ-loaded NPs were all in the negative range, indicating the presenceof negatively charged functional groups on their surface.

TABLE 5 Exemplary Letrozole-loaded nanoparticle data on zeta potentialZeta Mobility Potential (μ/s)/ RMS Type Sample ID (mV) (V/cm) ResidualPALS Letrozole-loaded −8.92 −0.70 1.26E−02 NPs 001 - 5 PALSLetrozole-loaded −8.84 −0.69 1.22E−02 NPs 001 - 4 PALS Letrozole-loaded−8.73 −0.68 1.22E−02 NPs 001 - 3 PALS Letrozole-loaded −9.35 −0.731.29E−02 NPs 001 - 2 PALS Letrozole-loaded −9.88 −0.77 1.24E−02 NPs001 - 1 Mean: −9.14 −0.71 1.24E−02 Std Err: 0.21 0.02 1.29E−04 Std Dev:0.47 0.04 2.88E−04BSA Coating of Letrozole Nanoparticles

A solution of Letrozole-loaded nanoparticles (LTZ-loaded NPs) wasprepared by dissolving 15.2 mg (±0.1) of nanoparticles in 25 mLdistilled water. 100 μL of 1% BSA solution was added to 1 mL of theLetrozole-loaded nanoparticles solution. The solution then was incubatedfor 1 hr at 60° C. with shaking 350 rpm. The sample was then collectedand dried using rotary evaporator, weighed, labeled and stored at 4° C.

The above procedure was repeated with void nanoparticles to obtainBSA-coated nanoparticles.

Purification Method of BSA-Coated Nanoparticles (Void and Drug-LoadedNanoparticles)

The obtained white solid of letrozole-loaded nanoparticles was purifiedby dialysis. 100 μm membrane was placed on each side of 1,000 μL doublesided reservoir and was filled with 1 mL of the solution ofLetrozole-loaded nanoparticles and was placed in 250 mL of 0.06 M PBSwith stirring. The PBS solution was changed every three hours threetimes.

The procedure was repeated with void nanoparticles to purify BSA-coatedvoid nanoparticles. Data of exemplary void nanoparticles are exhibitedin Table 6 and Table 7.

TABLE 6 Exemplary void and BSA-coated nanoparticle data Eff. Diam. Poly-Baseline Type Sample ID (nm) dispersity Index DLS BSA-coated void NPs002 - 5 273.56 0.29 0.00 DLS BSA-coated void NPs 002 - 4 297.40 0.300.00 DLS BSA-coated void NPs 002 - 3 310.54 0.32 0.00 DLS BSA-coatedvoid NPs 002 - 2 290.71 0.33 0.00 DLS BSA-coated void NPs 002 - 1 291.460.30 0.00 Mean: 292.74 0.31 0.00 Std Err: 5.97 0.01 0.00 Std Dev: 13.340.02 0.00

TABLE 7 Exemplary Letrozole-loaded and BSA-coated nanoparticle data Eff.Diam. Poly- Baseline Type Sample ID (nm) dispersity Index DLS LTZ-loadedBSA-coated - 5 138.98 0.36 4.81 DLS LTZ-loaded BSA-coated - 4 151.350.35 8.33 DLS LTZ-loaded BSA-coated - 3 157.09 0.35 7.40 DLS LTZ-loadedBSA-coated - 2 165.61 0.36 6.46 Mean: 153.26 0.35 6.75 Std Err: 5.590.00 0.75 Std Dev: 11.18 0.01 1.50Particle Size and Size Distribution Measurement

The particle size and the size distribution were measured by dynamiclight scattering (DLS). The mean diameter of the PLA-PEG-PLA NPs varieddepending on the percentage of the emulsifier PVA used. It was observedthat the mean particle size was directly related to the concentration ofPVA used in the formula. For instance, the results presented in Table 8show a direct correlation between the particle size and the percentageof PVA used.

TABLE 8 Effect of varying the concentration of the emulsifying agent PVAon the particle size and on the polydispersity of LTZ-loaded PLA-PEG-PLANPs Particle Size Formulation % PVA (nm) PDI LTZ-Loaded NPs 3 188.750.135 LTZ-Loaded NPs 2 145.43 0.189 LTZ-Loaded NPs 1 119.13 0.224LTZ-Loaded NPs 0.5 107.59 0.246

Formulations tested in this work were within the size range of 120-200nm, and showed a relatively homogeneous size distribution as revealed bypolydispersity index values. In order to avoid elimination of NPs inspleen sinusoids and liver fenestrae and to effectively deliver the drugto the targeted tumor tissue, the size of loaded nanoparticles may notexceed 200 nm and may not be 6 nm or smaller to avoid rapid eliminationfrom blood stream. As a result, this work provides a suitable method tocontrol and tailor the size of NPs. FIG. 19 shows the variation of PVAconcentrations and its effect on particle size.

Coupling of Anti-Her2 to Letrozole PLA-PEG-PLA Nanoparticles

50 μL of anti-Her2 (antibody) solution was incubated with 200 μLLetrozole PLA-PEG-PLA nanoparticles (6.45×10⁻⁴) for one hour in at 40°C. Afterward, the solution was dialyzed to remove excess anti-Her2,using a single sided dialysis chamber and a nitrocellulose membrane cutoff 300 kDa. The sample has been dialyzed against 200 ml of PBS buffer,and the buffer has been discarded and changed three times every 2 hours.The final dialyzed sample has been analyzed using dynamic lightscattering to measure the particle size of anti-Her2 Letrozole-loadedPLA-PEG-PLA nanoparticles.

Therapeutic Effect of LTZ-Loaded PLA-PEG-PLA NPs on Breast Cancer Cells(MCF-7)

The LTZ-loaded NPs were incubated with MCF-7 (estrogen receptor positivebreast cancer cell line) for 72 hours. The cytotoxic effect of the LTZnanoformula on the cell lines was studied by looking at the levels ofgene expression of antiapoptotic genes, MAPK3 and c-MYC. LTZ-loaded NPscaused a down regulation in the expression of these two genes,suggesting that the LTZ-loaded NPs asserted the same effect as the freedrug on breast cancer cell.

RNA Isolation

The RNA was isolated using a PureLink® RNA mini kit (Ambion-LifeTechnologies, Carlsbad, Calif.) following the manufacturer'sinstructions. Purity of isolated RNA was determined by measuring ratioof the optical density of the samples at 260 and 280 nm using NanoDrop™8000 spectrophotometer.

cDNA Synthesis

Complementary DNA strands were synthesized using a high-capacity cDNAreverse transcription kit (Applied Biosystems™) according to themanufacturer's instructions. Aliquots containing 1 μg of total RNA wereused from each sample.

Gene Expression Profiling and Data Analysis

Real-time PCR for the anti-apoptotic genes, MAPK3 and c-MYC, wasperformed to ensure the delivery of the drug by the NPs system, comparedwith the free drug formula of Letrozole. Applied Biosystems 7900HT fastreal-time PCR System and TaqMan® Gene Expression master mix(ThermoFisherScientific, Foster City, Calif.) was used, then the geneexpression were quantitated using the delta-delta CT (ΔΔ^(CT)) methodand further re-calculated manually. Changes in gene expression wereillustrated as a fold increase or decrease. The data were normalized,across all plates, to the housekeeping gene: glyceraldehydes-3-phosphatedehydrogenase (GAPDH). Pre-designed primers MAPK3 (Hs00385075_m1), c-MYC(Hs00153408_ml) and GAPDH (Hs02786624_g1) were commercially obtainedfrom Applied Biosystems, Foster City, Calif.

Effect of Letrazole Treatment on MCF-7 for 72 Hours

The MCF-7 cells were incubated with the following samples for 72 hoursin separate wells: LTZ 0.5 nM, NP (nanoparticle) loaded with LTZ 0.5 nM,LTZ 1 nM, NP loaded with LTZ 1 nM, LTZ 2 nM, and NP loaded with LTZ 2nM. The gene expression results are shown in FIGS. 20 and 21. In FIG.20, each bar represents the expression of MAPK3 gene in the presence ofeach sample. In FIG. 21, each bar represents the expression of c-MYCgene in the presence of each sample.

Method of Drug Release Study

Known amounts of Letrozole PLA-PEG-PLA nanoparticles were dispersed by abath sonicator (Branson 3800) for 20 min with the release media (1.0 mLof phosphate buffer pH 7.2). An amount equivalent to 690 mcg of thenanoparticles in 1.0 ml of release media (1.2% sodium lauryl sulfate(SLS) in 7.2 phosphate buffer) was placed inside sealed cellulosedialysis tubing with cutoff of 12,000-14,000 Da (Carolina, N.C., US).The dialysis tubing was placed in a screw cap bottle with 19.0 mlrelease media and kept in a shaking water bath (GFL 1083) at 37° C. andmedium speed. At different time intervals, aliquots of 3.0 ml werewithdrawn and immediately restored with the same volume of fresh releasemedia. The amounts of LTZ released were assessed by double beam UVSpectrophotometer (Thermo-Evolution UV 60S, Thermo Scientific), whichwas set up at 310 nm for Letrozole versus a calibration curve preparedin the same buffer. FIG. 2 depicts the release rate of the drug from thenanoparticle.

The features of the presently disclosed nanoparticle include a stablenanoparticle employing a PLA-PEG-PLA triblock copolymer for the deliveryof Letrozole. The PLA-PEG-PLA nanoparticles are biocompatible andbiodegradable to contain the therapeutic. Further, the sustained releaseof Letrozole over 72 hours makes this prototype different thanpreviously reported nanoparticles. The nanoparticle represents a firstline breast cancer treatment that can be given to a patient twice weeklycompared with the available oral tablet currently prescribed once daily.

The invention claimed is:
 1. A nanoparticle having an interior space anda membrane surrounding the interior space, wherein the interior spacecontains letrozole that is encapsulated by the membrane, and themembrane comprises; a polylactide-block-poly(ethyleneglycol)-block-polylactide block (PLA-PEG-PLA) copolymer wherein a numberaverage molecular weight range of the PEG block is 800 Da to 3 kDa and anumber average molecular weight range of each of the PLA block is from 1kDa to 5 kDa, a polyvinyl alcohol polymer, bovine serum albumin incontact with the outer surface of the membrane, and anti-Her2 antibodyattached to the outer surface of the membrane.
 2. The nanoparticle ofclaim 1, wherein said nanoparticle provides sustained release ofletrozole over a period of 72 hours.
 3. The nanoparticle of claim 1,wherein the nanoparticle comprises 60 to 95 weight percent of thepolylactide-block-poly(ethylene glycol)-block-polylactide block(PLA-PEG-PLA) copolymer and 0.5 to 5 weight percent of polyvinyl alcoholpolymer relative to the total weight of the nanoparticle.
 4. Thenanoparticle of claim 1, wherein the bovine serum albumin is 0.5 to 8weight percent relative to the total weight of the nanoparticle.
 5. Thenanoparticle of claim 1, wherein the nanoparticle has a diameter of 300nm to 370 nm.
 6. The nanoparticle of claim 1, wherein a rate of releaseof the breast cancer therapeutic agent is a cumulative percent of 25% to75% in 24 hours to 96 hours.
 7. The nanoparticle of claim 1, wherein theanti-Her2 antibody is bound to the membrane via a biotin-avidin complex.8. The nanoparticle of claim 7, wherein the anti-Her2 antibody issourced from a rabbit.
 9. The nanoparticle of claim 1, wherein thenanoparticle has a diameter of from 310 nm to 350 nm.
 10. Thenanoparticle of claim 1, wherein the anti-Her2 antibody is conjugated tothe membrane.
 11. The nanoparticle of claim 1, wherein the breast cancertherapeutic agent consists letrozole.
 12. The nanoparticle of claim 1,wherein the breast cancer therapeutic agent is 0.5 to 10 weight percentrelative to the total weight of the nanoparticle.
 13. The nanoparticleof claim 1, wherein the nanoparticle has an internal volume of from 1picoliter to 1 nanoliter.
 14. The nanoparticle of claim 1, wherein thenanoparticle has a zeta potential of −7 mV to −20 mV.
 15. Thenanoparticle of claim 1, wherein the membrane further comprises adiblock copolymer.
 16. The nanoparticle of claim 15, wherein a weightpercent of the diblock copolymer relative to the total weight of thenanoparticle is 0.01% to 0.1%.
 17. The nanoparticle of claim 15, whereinthe diblock copolymer comprises one hydrophobic block polymer and onehydrophilic block polymer.
 18. The nanoparticle of claim 17, wherein thediblock copolymer comprises at least one hydrophobic polymer blockselected from the group consisting of polycaprolactone (PCL),polyvalerolactone (PVL), poly(lactide-co-glycolide) (PLGA), polylacticacid (PLA), polybutyrolactone (PBL), polyglycolide, andpolypropiolactone (PPL), and at least one hydrophilic polymer blockselected from the group consisting of polyethylene glycol (PEG),hyaluronic acid (HA), and poly-γ-glutamic acid (PGA).
 19. Thenanoparticle of claim 17, wherein a number average molecular weightrange of the hydrophobic block polymer and the hydrophilic block polymeris from 800 Da to 5 kDa.
 20. The nanoparticle of claim 1, wherein themembrane is prepared by a double emulsion method comprising mixing afirst emulsion with a second emulsion, wherein the first emulsion andthe second emulsion comprise polyvinyl alcohol as an emulsifying agent.